1,1-dimethylurea

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

July - August 2014

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

Qualifier:

according to guideline

Guideline:

other: Guidelines for the Testing of Chemical, SEPA, P.R. China No. 301B "CO2 EVOLUTION TEST" (May 2004).

GLP compliance:

yes

Remarks:

OECD principles of the Good Laboratory Practice (GLP) (as revised in 1997) and GB/T 22278-2008 Principles of the Good Laboratory Practice.

Specific details on test material used for the study:

- Analytical purity: 99.9 %
- Lot/batch No.: 301601

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge (adaptation not specified)

Details on inoculum:

Sources of activated sludge inoculums: A fresh sample of activated sludge was collected from Sitang Wastewater Treatment Center. The collected sludge was filtrated with 830 μm sieve to remove the coarse particles and the impurities on the surface were removed using precipitation method. And the sludge was washed with mineral medium. The suspended solids concentration was determined to be 3000 mg SS//L-5000 mg SS/L using dry weight method after suspending with the mineral nutrient medium. The sludge was pre-conditioned for 5 days at test temperature. Before the test, the mean concentration of the sludge was determined to be 3973 mg SS/L and pH was 7.21.

Duration of test (contact time):

28 d

Details on study design:

see "any other information on material and methods incl. tables"

Reference substance:

aniline

Preliminary study:

no data

Key result

Parameter:

% degradation (CO2 evolution)

Value:

91.64

Sampling time:

28 d

Details on results:

see "any other information on results incl. tables"

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

The results showed that the cumulative percentage biodegradation of 1,1-dimethylurea within 28 days was 91.64% .

Executive summary:

A study was conducted to determine the biodegradability of the 1,1-dimethylurea in aerobic aqueous medium and to evaluate its biodegradability in the environment. The study was performed in compliance with the OECD Guidelines for the Testing of Chemicals No. 301B " CO2 Evolution Test "(1992).

The results showed that the cumulative percentage biodegradation of 1,1-dimethylurea within 28 days was 91.64% .

The cumulative percentage biodegradation of the reference item (aniline) in activated sludge after 28 days was 87.81 %.

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

September 2013 - March 2014

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)

Qualifier:

according to guideline

Guideline:

other: The Guideline for the Testing of Chemicals 301F, Ready Biodegradability: Manometric Respirometry Test, MEP, China (2004).

GLP compliance:

yes

Remarks:

HJ/T 155-2004 the Guideline of Good Laboratory Practices on Chemical Testing, MEP, China

Specific details on test material used for the study:

Batch T20111104
Purity >= 99.5 %

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

The fresh activated sludge used in the test was collected from Wuzhong district urban area sewage treatment plant(Collectioned date: 2013-09-09). The address of the plant is No. 1, Baodai East Road, Suzhou city. The batch No. of inoculum was AS-20130909-01.
The activated sludge was washed with test medium after removing the suspended solids and coarse particles on the day of collection. Then the activated sludge was centrifuged at 1100 g for 10 minutes, and the supernatant was discarded. The process was repeated for 5 times. After that, 43.7677 g of the activated sludge (wet weight) was weighted and suspended with test medium to made up to 1 litre (the dry weight concentration was calculated to be 4 g/L based on the dry weight content of 9.14%). The inoculum suspension was aerated for 7 days at test temperature in the test.
The moisture content of the activated sludge was re-determined after pre-condtioned, and the average value was 7.84% which was repeated for 3 times.

Duration of test (contact time):

28 d

Initial conc.:

100 mg/L

Based on:

test mat.

Details on study design:

Concentration of test substance: 100 mg/L
Concentration of microbial inoculum: 30 mg/L, base on dry weight.
Temperature:22±2℃, Monitored once every day during the test period.
Incubation vessel: The volume of the BOD bottle was 500 mL with 164 mL of solution and the BOD measurement range of the apparatusis 0 to 400 mg/L.
Period: 28 days
Light: the test was conducted in dark

Reference substance:

benzoic acid, sodium salt

Preliminary study:

no data

Parameter:

% degradation (O2 consumption)

Value:

0.46

Sampling time:

14 d

Key result

Parameter:

% degradation (O2 consumption)

Value:

29.97

Sampling time:

28 d

Details on results:

See "any other information on results incl. tables"

Results with reference substance:

See "any other information on results incl. tables"

Theoretical Oxygen Demand (ThOD)

The results of ThOD in test suspension, procedurecontrol and toxicity control respectively are shown in Table1.

Table 1: ThOD in groups

Substance name	ThOD [mg/mg]	Test suspension		Procedure control		Toxicity control
		Concentration[mg/L]	ThOD [mg/L]	Concentration[mg/L]	ThOD [mg/L]	Concentration[mg/L]	ThOD [mg/L]
1,1-dimethylurea	1.09 （Based on NH3）	100	109 （Based on NH3）			100	276（Based on NH3）or 421（Based on NO3）
	2.54 （Based on NO3）	100	254 （Based on NO3）			100
Sodium benzoate	1.67			100	167	100

pH and Temperature

The pH of the contents of the flasks at the end of the test was in the range 6.0-8.5 (6.56 -7.38,Table 2). The temperature during the test period was in the range 20.7-21.5℃.

Table 2: Determination of pH

Test stage	Inoculum blank		Test suspension		Procedure control	Toxicity control
	Flask No.1	Flask No.2	Flask No.3	Flask No.4	Flask No.5	Flask No.6
At the end	7.24	7.16	6.78	6.56	7.38	7.10

Nitrification

The oxygen consumption induced by nitrification at the end of test is listed in table 3.

Table 3: Nitrification

Stage	Beginning of the test		End of the test
Flask No.	A	B	1	2	3	4
Nitrate（containnitrite） [mg /L N]	<<	<<	0.199	0.286	0.299^*	0.352^*
Nitrite[mg /L N]	0.003	0.002	0.001	0.002	0.192^*	0.195^*
Nitrate[mg /L N]	-0.003	-0.002	0.198	0.284	0.107^*	0.157^*
Oxygen depletionby Nitrate[mg/L]	-0.014	-0.009	0.905	1.298	48.899	71.749
Oxygen depletionbyNitrite[mg/L]	0.010	0.007	0.003	0.007	65.856	66.885
Oxygen depletionbynitrification[mg/L]	-0.003	-0.002	0.908	1.305	114.755	138.634
Increment of oxygen depletion by nitrification[mg/L]			0.912	1.308	114.757	138.636
Average increment of oxygen depletion by nitrification[mg/L]			1.110
oxygen depletion by nitrificationof test substance[mg/L]					113.647	137.526

Remark:“*”: This value was the determination value after dilutingthe solution for 100 folds.“＜＜” meansthe value was lower thanthe limit of detection, andwasregarded aszero.Oxygendepletionby Nitrate(mg/L)= Nitrate(mg N/L)*4.57;OxygendepletionbyNitrite(mg/L)=Nitrite(mg N/L)*3.43;

Biodegradation

The percentage biodegradation of test substance in duplicates were 0.46% and -2.11% (mean -0.83%) on day 14, and 25.78% and 34.15% (mean 29.97%) at the end of the test(on Day 28) (Table 4).

The percentage biodegradation of the toxicity control and the procedure controlwere40.14% and 94.61% respectivelyon day 14, and 81.65% and 96.26% respectively on day 28（Table 4), indicating that the test substance was not inhibitory and the test was valid.

Table 4: Biodegradation

Day N	Inoculum blank			Test suspension							Procedure control			Toxicity control
	b1	b2	bm	a1	a1-bm	D1%	a2	a2-bm	D2%	( D1%+D2%)/2	c	c-bm	D3%	d	d-bm	D4%
2	11.3	14.1	12.7	11.3	-1.4	-1.28	16.9	4.2	3.85	1.28	87.2	74.5	44.61	87.2	74.5	17.70
4	12.8	16.9	14.9	14.1	-0.8	-0.69	16.9	2.1	1.88	0.60	121	106.2	63.56	127	112.2	26.64
7	19.7	19.7	19.7	14.1	-5.6	-5.14	19.7	0.0	0.00	-2.57	155	135.3	81.02	141	121.3	28.81
9	22.5	25.3	23.9	16.9	-7.0	-6.42	22.5	-1.4	-1.28	-3.85	163	139.1	83.29	160	136.1	32.33
11	19.3	19.7	19.5	16.9	-2.6	-2.39	19.7	0.2	0.18	-1.10	169	149.5	89.52	169	149.5	35.51
14	21.5	22.5	22.0	22.5	0.5	0.46	19.7	-2.3	-2.11	-0.83	180	158.0	94.61	191	169.0	40.14
16	26.7	28.1	27.4	22.5	-4.9	-4.50	22.5	-4.9	-4.50	-4.50	189	161.6	96.77	250	222.6	52.87
18	26.9	28.1	27.5	25.3	-2.2	-2.02	25.3	-2.2	-2.02	-2.02	191	163.5	97.90	309	281.5	66.86
21	29.4	30.9	30.2	30.9	0.8	0.69	36.6	6.5	5.92	3.30	197	166.9	99.91	355	324.9	77.16
23	32.7	33.8	33.3	53.5	20.3	18.58	59.1	25.9	23.72	21.15	197	163.8	98.05	369	335.8	79.75
25	36.4	36.6	36.5	82.3	45.8	42.02	101	64.5	59.17	50.60	200	163.5	97.90	374	337.5	80.17
28	35.9	36.6	36.3	178	141.8	130.05	211	174.8	160.32	145.18	197	160.8	96.26	380	343.8	81.65
28*					28.1	25.78		37.2	34.15	29.97

Remark:“b₁” and “b₂” were the direct reading of Flask No.1 and 2 in inoculum blankby BOD meter, “a₁” and “a₂” were the direct reading of Flask No.3 and 4 in test suspension, “c” was the direct reading of the Flask No. 5 in procedure control, and “d” was thethe direct reading of the Flask No.6 in toxicity control. The unit is mg/L; “*” : this value was collected by Nitrification on day 28. The calculation of biodegradation in Toxicity control was based on ThOD_NO3because the result of the determination of the nitriteand nitrate in test suspension was indicated that the nitrification of test substance was happened.

Validity criteria fulfilled:

yes

Conclusions:

The mean percentage biodegradation of test substance 1,1-dimethylurea was 29.97% on day 28 under the current test condition.

Executive summary:

A study was performed to determine the ready biodegradablilty of 1,1 -Dimethylurea in a Manometric Respirometry Test according to OECD 301F over a period of 28 days.

A test substance solution of 100 mg/L was inoculated with activated sludge (30 mg/L dry weight) which was pre-conditioned for 7 days in the test medium and kept in the dark at 20.7 - 21.5 °C. Biodegradation was determined by analysis of oxygen consumption over the 28 -day test period. The concentration of the reference substance sodium benzoate was 100 mg/L in the Procedure control group. 100 mg/L of sodium benzoate and 100 mg/L of test substance were used in the Toxicity control group. The test condition in Procedure control and Toxicity control was the same as in the Test substance group.

The percentage biodegradation of test substance in duplicates were 0.46 % and -2.11 % (mean -0.83 %) on day 14, and 25.78 % and 34.15 % (mean 29.97 %) at the end of the test (on Day 28). The percentage biodegradation of the toxicity control and the procedure control were 40.14 % and 94.61 % respectively on day 14, and 81.65 % and 96.29 % respectively on day 28.

The mean percentage biodegradation of the test substance 1,1 -dimethylurea was 29.97 % on day 28 under the current test condition.

Description of key information

Two studies were performed to determine the ready biodegradablilty of 1,1-Dimethylurea.

The first was a Manometric Respirometry Test according to OECD 301F over a period of 28 days.The percentage biodegradation of test substance in duplicates were 0.46 % and -2.11 % (mean -0.83 %) on day 14, and 25.78 % and 34.15 % (mean 29.97 %) at the end of the test (on Day 28). The percentage biodegradation of the toxicity control and the procedure control were 40.14 % and 94.61 % respectively on day 14, and 81.65 % and 96.29 % respectively on day 28. The mean percentage biodegradation of the test substance 1,1 -dimethylurea was 29.97 % on day 28 under the current test condition.

A second study was performed in compliance with the OECD Guidelines for the Testing of Chemicals No. 301B " CO2 Evolution Test "(1992).The results showed that the cumulative percentage biodegradation of 1,1-dimethylurea within 28 days was 91.64%.The cumulative percentage biodegradation of the reference item (aniline) in activated sludge after 28 days was 87.81 %.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable